Isolation FAQ opens with tossing and turning for digital isolator design challenges? Everything you want to know is here!

“Concerning digital isolation know-how, we proceed to gather the difficulties you encounter when designing. We all know these questions and solutions are important for designers already utilizing digital isolation or seeking to transition from conventional optocoupler isolation to digital isolation, so we’re publishing a collection of articles to reply your questions and supply follow-up classes useful resource.

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Concerning digital isolation know-how, we proceed to gather the difficulties you encounter when designing. We all know these questions and solutions are important for designers already utilizing digital isolation or seeking to transition from conventional optocoupler isolation to digital isolation, so we’re publishing a collection of articles to reply your questions and supply follow-up classes useful resource.

Within the first article, we’ll focus on points surrounding the core isolation know-how itself. See in case your query has been answered under. The applet on the finish of the article can also be accompanied by a group of digital isolation white papers for studying. You probably have different inquiries to reply, please depart us a message within the remark space.

isolation know-how

Q: What's the distinction between capacitive digital isolation and optocoupler isolation?

A: Optocouplers work by sending gentle over a bodily distance to speak whereas offering isolation bodily. The logic enter generates input-side present, and the LED output transmits gentle via the molded compound layer to the receiving photodetector and output. Digital isolators use a silicon-based semiconductor know-how by which two built-in circuit chips and a high-voltage dielectric capacitor are constructed into the silicon course of. At Texas Devices (TI), digital alerts are transformed to the excessive frequency area and despatched via a capacitor-based SiO2 dielectric isolation layer.

Q: What are the technical enhancements in capacitive isolation know-how in comparison with earlier isolation applied sciences?

A: Capacitive isolation know-how brings many benefits over conventional applied sciences resembling optocouplers. Together with however not restricted to: longer life, stronger excessive voltage efficiency, area saving, larger working temperature, higher integration functionality, dependable life specification, low energy consumption.

Q: What dielectric supplies are utilized in digital isolation units?

A: Texas Devices (TI) capacitive digital isolators use silicon dioxide (SiO2) materials because the dielectric to create an isolation layer throughout the machine.

Q: What are the failure modes of isolation units?

A: In each “open” and “shorted” modes, all isolation methods might fail, relying on the excessive voltage occasion the isolator is uncovered to. To forestall failure, you will need to hold working throughout the protected limits within the isolator information sheet.

Q: Do the traits of optocouplers change at excessive and low temperatures?

A: A key parameter affected by temperature is the present switch ratio (CTR), which is the ratio of the output present to the enter present. Ideally, the CTR is 100%, nevertheless it varies with temperature as proven within the graph under. Due to this fact, with a purpose to preserve a sure CTR, designers should “over-engineer” with a purpose to preserve the identical degree of efficiency over the lifetime of the system. That is why optocouplers usually require larger enter currents (about 10mA, ahead present) to compensate for the degradation of CTR with temperature and time. Driving the optocoupler with excessive ahead present additionally shortens its lifetime, which has an extra adversarial impact on reliability.

Q: Some isolation units often require energy. If these energy provides are designed with this kind of know-how, can isolation nonetheless be achieved?

A: There are a lot of methods to construct an remoted energy provide, from totally discrete to totally built-in. Our transformer pushed merchandise such because the SN6505 can be utilized along with a transformer to create a small remoted energy provide with output currents as much as 1A. On this case, the transformer acts as an isolation within the system. Texas Devices (TI) additionally presents single-chip remoted energy options, such because the ISOW7741 resolution, which permits communication by combining an on-chip transformer to create an remoted energy provide with capacitive digital isolation channels.

Q: Will the price of digital isolation be decrease? How a lot will the worth of optocouplers go up with digital isolation?

A: Digital isolation know-how has come a great distance over the previous decade, rising efficiency whereas lowering prices. On the identical time, digital isolators have extra benefits in integration functionality and reliability, making the associated fee hole between the 2 applied sciences on the system degree of isolation design smaller and smaller.

Q: With a purpose to improve the stand up to voltage, will a number of Capacitors be related in collection?

A: Sure! That is one in all some ways TI has elevated the excessive voltage functionality of its isolators. The brand new isolation machine makes use of capacitive isolation layers on either side of the machine and gives larger isolation energy and extra isolation margin.

Keep tuned for our subsequent article. Questions on selecting the best isolator, isolation interface, and digital isolator design will likely be answered shortly.